[PATCH] PM: QoS: Add check to make sure CPU freq is non-negative

[PATCH] PM: QoS: Add check to make sure CPU freq is non-negative

[Shivnandan Kumar]

	CPU frequency should never be non-negative.
	If some client driver calls freq_qos_update_request with some
	value greater than INT_MAX, then it will set max CPU freq at
	fmax but it will add plist node with some negative priority.
	plist node has priority from INT_MIN (highest) to INT_MAX
	(lowest). Once priority is set as negative, another client
	will not be able to reduce max CPU frequency. Adding check
	to make sure CPU freq is non-negative will fix this problem.
Signed-off-by: Shivnandan Kumar <quic_kshivnan@quicinc.com>

---
 kernel/power/qos.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/kernel/power/qos.c b/kernel/power/qos.c
index ec7e1e85923e..41e96fe34bfd 100644
--- a/kernel/power/qos.c
+++ b/kernel/power/qos.c
@@ -531,7 +531,8 @@ int freq_qos_add_request(struct freq_constraints *qos,
 {
 	int ret;
 
-	if (IS_ERR_OR_NULL(qos) || !req)
+	if (IS_ERR_OR_NULL(qos) || !req || value < FREQ_QOS_MIN_DEFAULT_VALUE
+		|| value > FREQ_QOS_MAX_DEFAULT_VALUE)
 		return -EINVAL;
 
 	if (WARN(freq_qos_request_active(req),
@@ -563,7 +564,8 @@ EXPORT_SYMBOL_GPL(freq_qos_add_request);
  */
 int freq_qos_update_request(struct freq_qos_request *req, s32 new_value)
 {
-	if (!req)
+	if (!req || new_value < FREQ_QOS_MIN_DEFAULT_VALUE ||
+		new_value > FREQ_QOS_MAX_DEFAULT_VALUE)
 		return -EINVAL;
 
 	if (WARN(!freq_qos_request_active(req),
-- 
2.25.1

Re: [PATCH] PM: QoS: Add check to make sure CPU freq is non-negative

[Shivnandan Kumar]

Gentle reminder,

Thanks,

Shivnandan

On 6/23/2022 12:16 PM, Shivnandan Kumar wrote:
> 	CPU frequency should never be non-negative.
> 	If some client driver calls freq_qos_update_request with some
> 	value greater than INT_MAX, then it will set max CPU freq at
> 	fmax but it will add plist node with some negative priority.
> 	plist node has priority from INT_MIN (highest) to INT_MAX
> 	(lowest). Once priority is set as negative, another client
> 	will not be able to reduce max CPU frequency. Adding check
> 	to make sure CPU freq is non-negative will fix this problem.
> Signed-off-by: Shivnandan Kumar <quic_kshivnan@quicinc.com>
>
> ---
>   kernel/power/qos.c | 6 ++++--
>   1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/power/qos.c b/kernel/power/qos.c
> index ec7e1e85923e..41e96fe34bfd 100644
> --- a/kernel/power/qos.c
> +++ b/kernel/power/qos.c
> @@ -531,7 +531,8 @@ int freq_qos_add_request(struct freq_constraints *qos,
>   {
>   	int ret;
>   
> -	if (IS_ERR_OR_NULL(qos) || !req)
> +	if (IS_ERR_OR_NULL(qos) || !req || value < FREQ_QOS_MIN_DEFAULT_VALUE
> +		|| value > FREQ_QOS_MAX_DEFAULT_VALUE)
>   		return -EINVAL;
>   
>   	if (WARN(freq_qos_request_active(req),
> @@ -563,7 +564,8 @@ EXPORT_SYMBOL_GPL(freq_qos_add_request);
>    */
>   int freq_qos_update_request(struct freq_qos_request *req, s32 new_value)
>   {
> -	if (!req)
> +	if (!req || new_value < FREQ_QOS_MIN_DEFAULT_VALUE ||
> +		new_value > FREQ_QOS_MAX_DEFAULT_VALUE)
>   		return -EINVAL;
>   
>   	if (WARN(!freq_qos_request_active(req),

Re: [PATCH] PM: QoS: Add check to make sure CPU freq is non-negative

[Rafael J. Wysocki]

On Thu, Jun 23, 2022 at 8:47 AM Shivnandan Kumar
<quic_kshivnan@quicinc.com> wrote:
>
>         CPU frequency should never be non-negative.

Do you mean "always be non-negative"?

>         If some client driver calls freq_qos_update_request with some
>         value greater than INT_MAX, then it will set max CPU freq at
>         fmax but it will add plist node with some negative priority.
>         plist node has priority from INT_MIN (highest) to INT_MAX
>         (lowest). Once priority is set as negative, another client
>         will not be able to reduce max CPU frequency. Adding check
>         to make sure CPU freq is non-negative will fix this problem.
> Signed-off-by: Shivnandan Kumar <quic_kshivnan@quicinc.com>
>
> ---
>  kernel/power/qos.c | 6 ++++--
>  1 file changed, 4 insertions(+), 2 deletions(-)
>
> diff --git a/kernel/power/qos.c b/kernel/power/qos.c
> index ec7e1e85923e..41e96fe34bfd 100644
> --- a/kernel/power/qos.c
> +++ b/kernel/power/qos.c
> @@ -531,7 +531,8 @@ int freq_qos_add_request(struct freq_constraints *qos,
>  {
>         int ret;
>
> -       if (IS_ERR_OR_NULL(qos) || !req)
> +       if (IS_ERR_OR_NULL(qos) || !req || value < FREQ_QOS_MIN_DEFAULT_VALUE
> +               || value > FREQ_QOS_MAX_DEFAULT_VALUE)

Why do you check against the defaults?

>                 return -EINVAL;
>
>         if (WARN(freq_qos_request_active(req),
> @@ -563,7 +564,8 @@ EXPORT_SYMBOL_GPL(freq_qos_add_request);
>   */
>  int freq_qos_update_request(struct freq_qos_request *req, s32 new_value)
>  {
> -       if (!req)
> +       if (!req || new_value < FREQ_QOS_MIN_DEFAULT_VALUE ||
> +               new_value > FREQ_QOS_MAX_DEFAULT_VALUE)
>                 return -EINVAL;
>
>         if (WARN(!freq_qos_request_active(req),
> --

I agree that it should guard against adding negative values, but I
don't see why s32 can be greater than INT_MAX.

Also why don't you put the guard into freq_qos_apply() instead of
duplicating it in the callers of that function?

Re: [PATCH] PM: QoS: Add check to make sure CPU freq is non-negative

[Shivnandan Kumar]

Hi Rafael,


Thanks for taking the time to review my patch and providing feedback.

Please find answer inline.

Thanks,

Shivnandan

On 7/13/2022 12:07 AM, Rafael J. Wysocki wrote:
> On Thu, Jun 23, 2022 at 8:47 AM Shivnandan Kumar
> <quic_kshivnan@quicinc.com> wrote:
>>          CPU frequency should never be negative.
> Do you mean "always be non-negative"?
Yes,corrected subject now.
>
>>          If some client driver calls freq_qos_update_request with some
>>          value greater than INT_MAX, then it will set max CPU freq at
>>          fmax but it will add plist node with some negative priority.
>>          plist node has priority from INT_MIN (highest) to INT_MAX
>>          (lowest). Once priority is set as negative, another client
>>          will not be able to reduce max CPU frequency. Adding check
>>          to make sure CPU freq is non-negative will fix this problem.
>> Signed-off-by: Shivnandan Kumar <quic_kshivnan@quicinc.com>
>>
>> ---
>>   kernel/power/qos.c | 6 ++++--
>>   1 file changed, 4 insertions(+), 2 deletions(-)
>>
>> diff --git a/kernel/power/qos.c b/kernel/power/qos.c
>> index ec7e1e85923e..41e96fe34bfd 100644
>> --- a/kernel/power/qos.c
>> +++ b/kernel/power/qos.c
>> @@ -531,7 +531,8 @@ int freq_qos_add_request(struct freq_constraints *qos,
>>   {
>>          int ret;
>>
>> -       if (IS_ERR_OR_NULL(qos) || !req)
>> +       if (IS_ERR_OR_NULL(qos) || !req || value < FREQ_QOS_MIN_DEFAULT_VALUE
>> +               || value > FREQ_QOS_MAX_DEFAULT_VALUE)
> Why do you check against the defaults?
Want to make sure to guard against negative value.
>
>>                  return -EINVAL;
>>
>>          if (WARN(freq_qos_request_active(req),
>> @@ -563,7 +564,8 @@ EXPORT_SYMBOL_GPL(freq_qos_add_request);
>>    */
>>   int freq_qos_update_request(struct freq_qos_request *req, s32 new_value)
>>   {
>> -       if (!req)
>> +       if (!req || new_value < FREQ_QOS_MIN_DEFAULT_VALUE ||
>> +               new_value > FREQ_QOS_MAX_DEFAULT_VALUE)
>>                  return -EINVAL;
>>
>>          if (WARN(!freq_qos_request_active(req),
>> --
> I agree that it should guard against adding negative values, but I
> don't see why s32 can be greater than INT_MAX.
yes, checking against negative values will be sufficient.
I will share patch v2 with only check against negative values.
>
> Also why don't you put the guard into freq_qos_apply() instead of
> duplicating it in the callers of that function?
Because function  freq_qos_remove_request calls freq_qos_apply with 
PM_QOS_DEFAULT_VALUE which is actually negative.
So I do not want to break that.

Re: [PATCH] PM: QoS: Add check to make sure CPU freq is non-negative

[Rafael J. Wysocki]

On Wed, Jul 13, 2022 at 10:37 AM Shivnandan Kumar
<quic_kshivnan@quicinc.com> wrote:
>
> Hi Rafael,
>
>
> Thanks for taking the time to review my patch and providing feedback.
>
> Please find answer inline.
>
> Thanks,
>
> Shivnandan
>
> On 7/13/2022 12:07 AM, Rafael J. Wysocki wrote:
> > On Thu, Jun 23, 2022 at 8:47 AM Shivnandan Kumar
> > <quic_kshivnan@quicinc.com> wrote:
> >>          CPU frequency should never be negative.
> > Do you mean "always be non-negative"?
> Yes,corrected subject now.
> >
> >>          If some client driver calls freq_qos_update_request with some
> >>          value greater than INT_MAX, then it will set max CPU freq at
> >>          fmax but it will add plist node with some negative priority.
> >>          plist node has priority from INT_MIN (highest) to INT_MAX
> >>          (lowest). Once priority is set as negative, another client
> >>          will not be able to reduce max CPU frequency. Adding check
> >>          to make sure CPU freq is non-negative will fix this problem.
> >> Signed-off-by: Shivnandan Kumar <quic_kshivnan@quicinc.com>
> >>
> >> ---
> >>   kernel/power/qos.c | 6 ++++--
> >>   1 file changed, 4 insertions(+), 2 deletions(-)
> >>
> >> diff --git a/kernel/power/qos.c b/kernel/power/qos.c
> >> index ec7e1e85923e..41e96fe34bfd 100644
> >> --- a/kernel/power/qos.c
> >> +++ b/kernel/power/qos.c
> >> @@ -531,7 +531,8 @@ int freq_qos_add_request(struct freq_constraints *qos,
> >>   {
> >>          int ret;
> >>
> >> -       if (IS_ERR_OR_NULL(qos) || !req)
> >> +       if (IS_ERR_OR_NULL(qos) || !req || value < FREQ_QOS_MIN_DEFAULT_VALUE
> >> +               || value > FREQ_QOS_MAX_DEFAULT_VALUE)
> > Why do you check against the defaults?
> Want to make sure to guard against negative value.
> >
> >>                  return -EINVAL;
> >>
> >>          if (WARN(freq_qos_request_active(req),
> >> @@ -563,7 +564,8 @@ EXPORT_SYMBOL_GPL(freq_qos_add_request);
> >>    */
> >>   int freq_qos_update_request(struct freq_qos_request *req, s32 new_value)
> >>   {
> >> -       if (!req)
> >> +       if (!req || new_value < FREQ_QOS_MIN_DEFAULT_VALUE ||
> >> +               new_value > FREQ_QOS_MAX_DEFAULT_VALUE)
> >>                  return -EINVAL;
> >>
> >>          if (WARN(!freq_qos_request_active(req),
> >> --
> > I agree that it should guard against adding negative values, but I
> > don't see why s32 can be greater than INT_MAX.
> yes, checking against negative values will be sufficient.
> I will share patch v2 with only check against negative values.
> >
> > Also why don't you put the guard into freq_qos_apply() instead of
> > duplicating it in the callers of that function?
> Because function  freq_qos_remove_request calls freq_qos_apply with
> PM_QOS_DEFAULT_VALUE which is actually negative.
> So I do not want to break that.

OK